A prominent male broadcaster once suggested on air that we female journalists can get a bit "judgmental" at certain times of the month.

One of those times is when men make stupid statements about that time of the month.

Alasdair Thompson is probably wishing he had called in sick last week. The Employers and Manufacturers Association (Northern) chief wasn't at his most productive after a few late nights, and was still half asleep when Newstalk ZB rang him for his pre-arranged interview with Mike Hosking.

That's how he ended up basically saying that one of the reasons for our 12 per cent gender pay gap is that women are less productive because we menstruate, or as he quaintly put it, "have sick problems".

"Women do, in general [take more sick leave], why? Because once a month they have sick problems."

Oh yeah, and we also tend to have babies who seem to require productivity-sapping attention every now and again.

Cue the near-universal outrage and disgust from all corners of the political spectrum. You have to hand it to Alasdair. Few things have so united such a broad group of Kiwi women.

Kate Wilkinson wondered if he'd had a "brain explosion", Paula Bennett said he sounded like a dinosaur, and former Prime Minister Dame Jenny Shipley fired off a letter questioning Thompson's "absurd and demeaning arguments".

As Shipley wrote: "It is not only socialists who think that people of equal talent deserve to be paid for equal effort!"

To be fair, Thompson has been at pains to stress that the EMA and he personally are staunch supporters of equal pay for "equal productivity".

It's just that, as Wellington lawyer Mai Chen put it: "If you mistakenly think that because a person is a woman and therefore will have periods and will therefore spend time in the bathroom or at home not being able to work because they're so incapacitated - then you may value them less than a male employee and may pay them less."

Thompson might have avoided being the target of tampon-throwing protesters if he had framed his argument a little differently and admitted that his assertions didn't actually carry the weight of empirical "fact" as he had made out but was based on the limited experience of his own office and some of the employers he represents.

But Thompson couldn't seem to help himself. He was sorry if people took offence but he kept insisting he was right. Unfortunately for him, he vastly overestimated his media skills, and his attempts at bossing his way through interviews with a couple of female TV3 reporters just made him look smug and domineering.

This is not to say that there are not women out there who don't have problems with their periods severe enough to require days off. But there's no evidence that this qualifies as a problem significant enough to affect women's average pay rates.

Public Service Association records show that on average, women in Government jobs take just 1.6 sick days more a year than men, which is low considering most women still carry the burden of childcare.

Thompson did subsequently supply one paper to back his claim, from a study of employees of an Italian bank, but the researchers' conclusion that female absences were due to menstrual problems was based on the researchers' own interpretation of the records, rather than employees declaring that to be the case.

Still, Thompson has done us a favour by forcing the spotlight on pay equity, an issue that struggles for public attention.

What's behind women's persistently lower earnings? Even after controlling for variables like education, experience, race and choice of occupation, about 12 per cent of the pay gap remains unexplained.

It's true that women often take time off paid work to start a family or look after children (and I am one of them). How employers handle that fact of life is as important to productivity as taking time off in the first place.

I know of one boss who suggested to a young lawyer in his employ that she leave her newborn in the nursery during the day while she returned to the office to finish the work she had interrupted to give birth.

She did so, and for reasons that still seem mysterious to him, she had a meltdown after a few days. Women. They have babies. They menstruate.

A recent study has shown that the gender pay gap starts early. One possible reason is that generally men are much more assertive in negotiating higher starting salaries and pay rises.

But the same qualities that make many women less likely to demand higher pay may be what also make women a civilising influence. The research shows that companies which promote more qualified women to senior levels of management and boards outperform others on average. It's been suggested, too, that more women might have saved us from the testosterone-driven excesses that led to the global financial crisis.

Women may operate differently. The challenge for employers, as Jenny Shipley notes, is how to nurture and retain talent "by salary recognition and workplace flexibility, not [Thompson's] absurd explanation as to why wage differences linger".